To provide the power required to support the flight capabilities of helicopters, the main rotors of helicopters incorporate a plurality of main rotor blades having large radial dimensions. The large radial dimensions of helicopter rotor assemblies results in helicopters having large structural envelopes that occupy an inordinate amount of space. For example, an Apache helicopter, has a main rotor with four main rotor blades, a rotor diameter of approximately 48 feet (each main rotor blade has a length of approximately 21 feet), a fuselage length of approximately 49 feet, an overall length of approximately 58 feet and a height of nearly 17 feet. It is often desirable to reduce the structural envelopes of such helicopters to facilitate rapid deployment, routine transport, stowage, and/or to reduce the vulnerability thereof to environmental conditions.
Several options are available to reduce the structural envelopes of helicopters. One option is to design the main rotors of helicopters so that the main rotor blades may be removed from the rotor hub assembly (i.e., the main rotor assembly). While this is a viable solution in some circumstances, it should be appreciated that such main rotors may be unnecessarily complex. In addition, it should be appreciated that removal of the main rotor blades tends to be time consuming and labor intensive. Moreover, these same time constraints and labor requirements exist when the helicopter is reconfigured for subsequent flight operations. Further, removal of the main rotor blades may require rebalancing of the blades upon reattachment. Therefore, reduction of the structural envelope of helicopters by removal of the main rotor blades may not be the most viable option under some circumstances.
Another option available to reduce the structural envelopes of helicopters is to design the main rotor assemblies thereof so that the main rotor blades may be folded about the main rotor hub assembly. Main rotor blade folding operations may be implemented either automatically via hydraulic systems or manually. However, in helicopter rotors having four main rotor blade, the prior art methods of folding have not sufficiently reduced the structural envelope.